Irritable Bowel Syndrome
A common functional GI disorder causing recurrent abdominal pain associated with changes in stool frequency or form, managed with diet, stress reduction, and symptom-directed medications.
Emergency Management: Severe, sudden onset abdominal pain, especially if associated with vital sign abnormalities or peritoneal signs, warrants immediate ED evaluation to rule out acute abdomen (e.g., perforation, ischemia).
Irritable Bowel Syndrome (IBS) is a functional gastrointestinal disorder characterized by chronic abdominal pain and altered bowel habits in the absence of an identifiable organic cause. It is considered a disorder of gut-brain interaction. Symptoms typically involve diarrhea, constipation, or a mixture of both.
Detailed Overview
IBS is one of the most common functional GI disorders, significantly impacting patients' quality of life. The pathophysiology is complex, involving visceral hypersensitivity, altered gastrointestinal motility, intestinal inflammation, and alterations in the gut microbiome. Diagnosis relies on symptom-based criteria, specifically the Rome IV criteria, after excluding warning signs. Management requires a biopsychosocial approach, including dietary modifications, targeted pharmacotherapy based on the predominant bowel habit, and behavioral therapies.
Epidemiology & Demographics
Global prevalence is estimated at 5% to 10%. It is 1.5 to 2 times more common in women than in men. Peak age of onset is typically between 20 and 30 years old, with prevalence decreasing in those over 50 years of age.
Etiological Mechanism
The exact etiology is unknown but is multifactorial. It involves dysregulation of the gut-brain axis, genetic predisposition, and often follows a severe gastrointestinal infection (post-infectious IBS).
Primary Causes
While a single root cause is absent, primary triggers include prior acute gastroenteritis (Campylobacter, Salmonella), psychosocial stress, food intolerances (FODMAPs), and gut microbiome dysbiosis.
The core mechanisms involve visceral hypersensitivity, where normal bowel distension is perceived as painful due to altered central nervous system processing or sensitized enteric nerves. Altered GI motility leads to accelerated transit (IBS-D) or delayed transit (IBS-C). Increased intestinal permeability and low-grade mucosal inflammation, particularly increased mast cells in the terminal ileum and colon, contribute to symptom generation. Microbial dysbiosis alters fermentation of carbohydrates, producing excess gas and short-chain fatty acids.
Diagnostic Criteria & Guidelines
Rome IV Criteria: Recurrent abdominal pain, on average, at least 1 day/week in the last 3 months, associated with 2 or more of the following: 1) Related to defecation, 2) Associated with a change in frequency of stool, 3) Associated with a change in form (appearance) of stool. Symptoms must have started at least 6 months prior.
For IBS-C: Psyllium husk 5-10g/day, Polyethylene Glycol (PEG) 17g/day. For IBS-D: Loperamide 2mg 45 min before meals (up to 16mg/day). For Pain: Dicyclomine 10-20 mg PO QID or Hyoscyamine 0.125-0.25 mg PO TID-QID.
Second-Line & Adjunctive Therapy
For IBS-C: Linaclotide 290 mcg PO daily. For IBS-D: Eluxadoline 100 mg PO BID or Rifaximin 550 mg PO TID for 14 days. For refractory pain: Amitriptyline 10-25 mg PO at bedtime.
Surgical & Procedural Management
None indicated.
Patient Counseling & Advice
Reassure the patient that IBS is a chronic but benign condition that does not increase the risk of colon cancer. Emphasize the strong connection between stress, anxiety, and GI symptoms, and the importance of dietary compliance.
Follow-Up & Monitoring Schedule
Follow-up every 4-8 weeks when initiating new dietary therapies or pharmacotherapy to assess response using validated tools like the IBS-Symptom Severity Scale (IBS-SSS).
Preventive Strategies
Cannot be entirely prevented, but symptom flare-ups can be minimized through strict adherence to individualized dietary plans and stress-reduction techniques.
Chronic, relapsing-remitting course. Although it does not affect life expectancy, it can significantly impair quality of life if unmanaged. 50-70% of patients achieve satisfactory symptom control with combination therapy.